var http_request = false;
function send_request(url) {//初始化、指定处理函数、发送请求的函数
		http_request = false; 
		 
		//开始初始化XMLHttpRequest对象
		if(window.XMLHttpRequest) { //Mozilla 浏览器
			http_request = new XMLHttpRequest();
			if (http_request.overrideMimeType) {//设置MiME类别
				http_request.overrideMimeType('text/xml');
			}
		}
		else if (window.ActiveXObject) { // IE浏览器
			try {
				http_request = new ActiveXObject("Msxml2.XMLHTTP");
			} catch (e) {
				try {
					http_request = new ActiveXObject("Microsoft.XMLHTTP");
				} catch (e) {}
			}
		}
		if (!http_request) { // 异常，创建对象实例失败
			window.alert("不能创建XMLHttpRequest对象实例.");
			return false;
		}
		http_request.onreadystatechange = processRequest;
		// 确定发送请求的方式和URL以及是否同步执行下段代码
		http_request.open("GET", url, false);
		http_request.send(null);
	}
	// 处理返回信息的函数
	function processRequest()
	 {
	    if (http_request.readyState == 4)
	     { // 判断对象状态
	        if (http_request.status == 200)
	         { // 信息已经成功返回，开始处理信息
	         	 returnContent = http_request.responseText; 
	              if(""!= returnContent)
   		 		 	document.getElementById("content").innerHTML=returnContent;
		    	  
	         }
	        else 
	         { //页面不正常
	            alert("您所请求的页面有异常。");
	         }
	    } 
	 }